Networking Examples - Subnets and Overlay

[JamesHK44]

This isn't quite just specific to NSX-T but one confusion I have is how to properly configure subnets that would be used for the encapsulation networks. This is sort of a mix of a question between VMware NSX as well as physical networking configuration. What I am trying to find is a good example of what are often used. I find design guides specific to VCF and NSX-T which breaks down the management clusters into some examples. Normally, it will have a larger /16 that is broken down into /24 subnets and used for VLAN purposes. I use these references and have those subnets available on top of rack nexus switches. For example:

VLAN 1611 Management - 172.16.11/0/24
vMotion 1612 Network - 172.16.12.0/24
vSAN 1613 Network - 172.16.13.0/24

These subnets gateways are normally pointing to a VIP that is part of the Top of Rack switches which makes understanding the routing sensible. Now with NSX-T when you have a Tier-1 router with multiple segments for VMs to be placed on, how are these normally configured on your physical network so everyone can route to these newly created networks?

My understanding is that if I want to take a /24 that will be on a Geneve overlay network and create a new segment for that, the T1 will be the gateway and NSX-T will be configured with your BGP on the Tier-0 but how exactly does this become routable on the rest of your network?

Any insight on what I should be referencing would be a big help.

[Sreec]

You must consider your TEP connectivity requirements and predictable growth for ESXI and Edges when you size Overlay Subnets based on the design. That being said /23 or /24 would be sufficient for most of the platforms and these subnets must not overlap with another network.  Also, I think you are a bit confused with overlay network and workload subnets, based on the application requirements you need to size workload subnets(these subnets are unique to workload ) and assume the gateway is configured on NSX-T T1 Router you can easily route these subnets via VRF/T0 configuration. In a nutshell, workloads will need subnets and gateway, Overlay subnet is needed for Host and Edges and Underlay Connectivity subnets is also needed for VRF/T0 to connect to upstream routers for exchanging routes.

https://nsx.techzone.vmware.com/resource/nsx-t-reference-design-guide-3-0#_Toc59008623

 

[Smith052]

Thanks for sharing this info this is useful keep it up.

onevanilla